Thinning Increases Diameter Growth of Paper Birch in the Susitna Valley, Alaska: 20 Year Results

A uniform stand of paper birch, age 44 yr, in the Susitna Valley, Alaska, was thinned to four spacings: control (6.4 ft), 16 ft, 20 ft, and 24 ft. After 20 yr, survival of crop trees was 99%. Diameter growth was positively related to spacing. Height growth was apparently unaffected by spacing. Height to the first branch and other outward indicators of stem quality were unaffected by spacing. Cubic foot volume per acre was highest for the unthinned control, but volume per tree increased following thinning. Recommendations about spacing for paper birch in Alaska will depend on the type of forest outputs sought. North. J. Appl. For. 15(3):113-115.